In order to protect the environment of the earth or to improve a fuel consumption rate (fuel economy), a vehicle having an idling stop function and a deceleration regeneration function has been developed. Such a vehicle is provided with a power supply in which an electric storage stores regenerative power generated by a generator and that supplies power of the electric storage or power of a battery (DC power supply) to a load when the vehicle is decelerated.
For example, in a power supply illustrated in Japanese Unexamined Patent Application Publication No. 2011-155791 or a power supply illustrated in FIG. 7 of Japanese Patent No. 4835690, a switch is provided in a power path between a load (narrow voltage range auxiliary) which requires protection so as not to decrease a supply voltage and a battery. Furthermore, an electric storage is connected to a power path between the load and the switch through a DC-DC converter. A generator, a starter motor, or another load (auxiliary, wide voltage range auxiliary) is connected to the power path between the battery and the switch.
For example, when the regenerative power is generated by the generator due to deceleration of the vehicle, the switch is turned on and the DC-DC converter charges the electric storage by the regenerative power. In addition, if the vehicle is in a state other than an idling stop, when the regenerative power is not generated by the generator, the switch is turned on and the DC-DC converter discharges the electric storage. In this case, in Japanese Unexamined Patent Application Publication No. 2011-155791, the DC-DC converter discharges the electric storage until a voltage by which the DC-DC converter can be operated and the electric storage can continuously drive the load over a predetermined period of time in which the voltage of the battery is lowered momentarily.
When restarting an engine after the idling stop of the vehicle, the starter motor is actuated and thereby a large current flows through the starter motor and the voltage of the battery is lowered momentarily. Thus, in this case, the switch is turned off, the load and the electric storage are electrically disconnected from the battery and the starter motor, and power of the electric storage is supplied to the load through the DC-DC converter. Thus, the load is stably and continuously driven by power of the electric storage.